1. Field of the Invention
The present invention relates to a device for controlling drift of a vehicle during cornering, which drift is intentionally caused by sideslip of accelerated rear driving wheels for directing the vehicle into a desired course rapidly. This kind of drift is usually called power drift.
2. Description of the Prior Art
An example of a power drift control device for a vehicle is disclosed in Japanese Patent Provisional Application No. 62-275814. During cornering, particularly sharp or rapid cornering, a vehicle is subjected to lateral acceleration. Load movement thus occurs between the laterally spaced wheels.
The power drift control device controls the load movement between the wheels in such a manner that larger load movement occurs between the rear wheels while smaller load movement occurs between the front wheels, whereby to make smaller the total cornering force of the rear wheels than that of the front wheels. By this, a yaw moment in the direction of causing oversteer is produced, thus making it easy to attain power drift, i.e., attain sideslip or drift of the rear driving wheels by acceleration during cornering.
The prior art device is adapted to determine the above distribution of the load movement, i.e., the yaw moment in the direction of causing oversteer on the basis of driving force or acceleration only. This cannot always meet the requirement.
For example, though acceleration of the vehicle is constant, more rapid turn is required as the steering wheel angle becomes larger, i.e., a larger yaw moment in the direction of causing oversteer is required. The prior art control device, however, is not responsive to the steering wheel angle, thus causing a problem that desired power drift cannot be attained when the steering wheel angle is large, e.g., in case of a vehicle tending to understeer it becomes impossible to attain power drift of itself.
However, if the control device is designed so that a large yaw moment in the direction of causing oversteer can be produced by acceleration, the yaw moment becomes too large in a small steering wheel angle range to cause an unstable behavior of a vehicle as swerving.